PAC privilege escalation using Function.prototype.call — Mozilla

mozbugra4 reports that a malicious Proxy AutoConfig PAC server could serve a PAC script that can execute code with elevated privileges by setting the required FindProxyForURL function to the eval method on a privileged object that leaked into the PAC sandbox. By redirecting the victim to a...

EvalInSandbox escape (Proxy Autoconfig, Greasemonkey) — Mozilla

Mozilla researcher mozbugra4 demonstrated that javascript run via EvalInSandbox can escape the sandbox and gain elevated privilege by calling valueOf on objects created outside the sandbox and inserted into it. Malicious scripts could use these privileges to compromise your computer or data...